1. Field of the Invention
This invention relates to a surgical tool and method for preparing a bone site for implantation of an orthopedic endoprosthesis having anti-rotational components as well as facilitating pre-implantation alignment of the prosthesis. More particularly, the invention relates to aligning and implanting a femoral component of a total hip joint or a humeral component of a shoulder joint. However, it may also be used to align and implant femoral and tibial components of a prosthetic knee joint.
The method and surgical tool that is used to open and form the bone canal also facilitates pre-implantation alignment of the prosthesis using trial components, as well as preparation of the bone site for anti-rotational implantation of the prosthesis. Most commonly, this invention would be employed in connection with the implantation of prostheses into long bones, but it would not be limited thereto. The quantity of medical instruments, as well as the time and number of movements required in forming a bone canal and conducting pre-implantation alignment of the prosthesis using trial components is reduced with the use of this surgical tool. Also, the risk of rotational failure of the prosthesis is reduced when it is implanted into a bone canal that is shaped to accept it's anti-rotational features.
As used herein, when referring to bones or other body parts, the term “proximal” means closest to the heart, and the term “distal” means more distant from the heart. When referring to tools and instruments, the term “proximal” means closest to the practitioner, and the term “distal” means distant from the practitioner.
2. Description of Related Art
Proper alignment of orthopedic implants, such as joint replacement prostheses, is essential to the success of surgical procedures involving replacing damaged joints. Such prostheses commonly include stems for insertion into the canals of long bones. A stem is used to anchor the prosthesis in a bone cavity.
A bone cavity is commonly prepared by forming a hole in the bone, such as by drilling or reaming, and creating an opening sized and contoured to receive the stem of the prosthesis. The stem is inserted into the bone cavity, and optionally, a joint bearing member may be attached or coupled to the stem, with the joint bearing member extending out of the bone cavity.
Typically, once a stem that is coupled to a femoral component, for example, is inserted into a prepared bone cavity, it is necessary to rotate the stem to properly orient it. Sometimes, the stem must be removed and reinserted, which may damage the bone cavity and surrounding bone, as well as increase intra-operative time.
To achieve pre-implantation alignment of the prosthesis, the prosthesis stem is typically manipulated, and the desired position identified, by marking the bone and the stem. Subsequent alignment during implantation is then achieved by using the marks to align the stem with respect to the bone. The drawback to this method is the potential imprecision in the alignment. Because the marks on the stem and bone are not in close proximity to each other, parallax and other problems associated with alignment by eye may result. Also, the stem may move from its aligned position as it is inserted.
Misalignment of an implanted prosthesis in the human body is an undesirable result in joint replacement surgery. To alleviate implant misalignment, past efforts have been directed toward providing some pre-implantation trialing and marking methods that strive to achieve an implanted prosthesis having the optimal orientation.
One such effort is presented in U.S. Pat. No. 4,678,471 to Noble et al., entitled “Method and Apparatus for Preventing Rotational Failure of Orthopedic Endoprostheses”. Noble et al. relates to an apparatus for making at least one groove in a medullary canal in a bone. The apparatus is an elongate member having a flattened head portion and a stem, and having one channel that receives a cutting tool for cutting a groove in the canal, remote from the resected bone surface.
Another effort is presented in U.S. Pat. No. 5,053,037 to Lackey, entitled “Femoral Instrumentation for Long Stem Surgery”. Lackey relates to a bone cutting block in conjunction with a reamer, for forming the end of a long bone.
Yet another effort is presented in U.S. Pat. No. 6,206,884 to Masini, entitled “Reduction-Based Joint Replacement Apparatus and Methods”. Masini relates to a reduction-based orthopedic system facilitating the installation of a properly oriented prosthetic component. Separate elements of the system for trialing and marking the bone include an anchoring unit, a trialing component, and a cutting guide.
Despite these efforts, there is still a continuing need for improving tools and methods for preparing a bone site for implantation of a prosthesis having anti-rotational components as well as facilitating pre-implantation alignment of the prosthesis.
It is therefore an object of the present invention to provide a surgical tool which facilitates reaming a bone canal, attaching and manipulating a trial component, and marking the rotational alignment of the trial component on the bone.
It is a further object of the present invention to provide a surgical tool which facilitates engagement to various tools and components for the purposes of both reaming a bone canal as well as facilitating trialing.
It is yet another object of the present invention to provide a surgical tool for cutting keyways in the bone once the rotational alignment of the trial component is determined.